Field of the Invention
The present invention relates to a toner and a two-component developer to be used in an electrophotographic system, an electrostatic recording system, an electrostatic printing system, a toner jet system, or the like.
Description of the Related Art
In recent years, additional improvements in speed and image quality, additional energy savings, and the like have been required in association with the widespread use of a full-color copying machine of an electrophotographic system. A toner that can be fixed at an additionally low fixation temperature in order that power consumption in a fixing step may be reduced has been studied as a specific technology for the energy savings. A toner using a crystalline resin as its softening agent has been studied in order that the toner that can be fixed at low temperature may be realized.
When the crystalline resin is used as a binder resin for the toner, its low-temperature fixability improves but its elasticity at high temperature reduces and hence the so-called hot offset phenomenon in which the toner adheres to a fixing member (such as a fixing roller or a fixing belt) occurs in some cases.
Japanese Patent No. 04047134 proposes a toner that achieves compatibility between its low-temperature fixability and hot offset resistance. When a crosslinking component is produced by using an oxyalkylene ether compound (alkylene oxide adduct) of a novolac type phenol resin, a distance between a crosslinking point and another crosslinking point lengthens (a molecular weight between the crosslinking points increases). In this case, molecular motion by heat easily occurs and a flexible crosslinked body is easily produced. Accordingly, the hot offset resistance can be maintained without any reduction in the low-temperature fixability.
In recent years, multimedia compatibility by virtue of which the toner can be used for various recording materials (media) such as a postcard, small-sized paper, an envelope, cardboard, and label paper has also been required. In view of the foregoing, it has been required to improve the hot offset resistance while maintaining the low-temperature fixability even when any one of the various recording materials is used. This is because a hot offset is liable to occur when a large-sized recording material is passed through a fixing member after a small-sized recording material has been passed therethrough. The reason why the hot offset is liable to occur is as described below. A temperature increase occurs in a portion on the fixing member through which no recording material has passed owing to the passage of the small-sized recording material, and hence the toner on the large-sized recording material to be subsequently passed through the fixing member is excessively heated.